1. Field of the Invention
This invention relates to a windscreen wiper, which is also known as a windshield wiper.
2. Description of the Related Art
The invention relates in particular to a windscreen wiper which has a curved backbone and which may have a varying width and/or thickness. It will be appreciated by those skilled in the art that the backbone may be in the form of a beam that is curved in a plane or may have a compound curvature such as in EP-A-0528 643 and DE-A-196 51229. The beam will have width and thickness dimensions. The beam will also have a radius of curvature at each point along its length.
The applicant has conducted substantial analysis and experimentation and believes that he has found a relationship between the width, the beam material's Young's modulus and the total length of the beam and the thickness, the beam material's Young's modulus and the total length, which provides a windscreen wiper that operates in an improved manner.
In this specification, the term “spatially consolidated” is to be understood, unless the context clearly indicates otherwise, to mean that the actual perimeters of a cross-section coincides with the shortest possible perimeter encapsulating that cross-section.
According to a first aspect of the invention there is provided a windscreen wiper which includes                an elongate curved backbone which is of a resiliently flexible material having a Young's modulus of between 50 to 350 GPa, the backbone having a substantially spatially consolidated cross-sectional profile at substantially all points along its length, in which the magnitude of the width at substantially the widest point along the backbone, Wm (expressed in millimeters) is at most (−8.889.10−5*E+0.05378)*L−5.25, where L is the total length of the backbone expressed in millimeters and E is the Young's modulus of the backbone material expressed in GPa.        
Further according to this aspect, there is provided a windscreen wiper which includes                an elongate curved backbone which is of a resiliently flexible material having a Young's modulus of between 50 to 350 GPa, the backbone having a substantially spatially consolidated cross-sectional profile at substantially all points along its length, in which the ratio of the magnitude of the width at substantially the widest point along the backbone, to the total length L of the backbone, Rw is at most (−8.889.10−5*E+0.05378)−5.25/L, where L is the total length of the backbone expressed in millimeters and E is the Young's modulus of the backbone material expressed in GPa.        
According to a second aspect of the invention there is provided a windscreen wiper which includes                an elongate curved backbone which is of a resiliently flexible material having a Young's modulus of between 50 to 350 GPa, the backbone having a substantially spatially consolidated cross-sectional profile at substantially all points along its length, in which the magnitude of the thickness at substantially the thickest point along the backbone, Tm (expressed in millimeters) is at most 0.0007*L−0.0027407*E+1.37814, where L is the total length of the backbone expressed in millimeters and E is the Young's modulus of the backbone material expressed in GPa.        
Further according to this aspect, there is provided a windscreen wiper which includes                an elongate curved backbone which is of a resiliently flexible material having a Young's modulus of between 50 to 350 GPa, the backbone having a substantially spatially consolidated cross-sectional profile at substantially all points along its length, in which the ratio of the magnitude of the thickness at substantially the thickest point along the backbone to the total length L of the backbone, Rt is at most 0.0007−(0.0027407*E−1.37814)/L, where L is the total length of the backbone expressed in millimeters and E is the Young's modulus of the backbone material expressed in GPa.        
The material of the backbone may be a composite material. In this case, the Young's modulus will be that of the composite material.
The total length of the backbone may be between about 300 mm to 1200 mm.
The backbone may have a varying width and or thickness, along its length. The backbone may have a free form curvature in a plane or may have a compound curvature (that is, curved in two planes).